Candidate. My immediate goal is to develop the skills and expertise essential for me to become a successful independent investigator. My long-term goal is to contribute to a comprehensive understanding of the innate immune control of viral infections, and to use this knowledge to help create novel therapies for viral diseases. To achieve these goals, I will use my background as a trained clinician and a developed research scientist. I acquired my M.D. degree from National Taiwan University in 2000, finished my clinical training in 2004, and received my Ph.D. degree from Harvard University in 2008. My Ph.D. dissertation focused the enzymatic regulation of the entry processes of influenza A virus (IAV) and SARS coronavirus. These studies allowed me to develop an RNAi screen with Dr. Stephen Elledge for factors that modulate IAV replication. This screen identified a family of interferon-inducible transmembrane (IFITM) proteins critical to the interferon-mediated control of several pathogenic viruses, including IAV, dengue virus and West Nile virus. The study of the activities and mechanisms of these important proteins is the basis of my research proposal and my scientific goals in the next several years. Environment and Career Development Plan. My development plan focuses on three directions that will most strengthen my abilities as a successful independent investigator. (1) I will enhance my intellectual background in innate immunity and my experience in novel technologies important to my scientific goals. To do so, I will access the many seminars, classes and other resources available to me at the New England Primate Research Center (NEPRC), Harvard Medical School, the New England Regional Center of Excellence/Biodefense and Emerging Infectious Diseases (NERCE/BEID), and the Broad Institute of Harvard and MIT. (2) I will further develop experience necessary for conducting independent animal studies. Here I will rely on the exceptional expertise and formal training provided by the NEPRC. (3) I will improve my communication, manuscript preparation, grant-writing, lab management, and mentoring skills. These skills will be developed through formal classes provided by Harvard University, by participation in the multiple undergraduate and graduate training programs, and through direct experience with the guidance of my mentor and the scientific leadership at the NEPRC. Research Program. Our previous studies indicate that the IFITM proteins are critical mediators of the immune control of IAV and several other human pathogens. They are unique as viral restriction factors because they prevent infection by inhibiting viral entry. Our overall goal is to understand comprehensively the activities and mechanisms of these proteins. These studies are organized into three specific aims. Aim 1 characterizes these proteins biochemically and functionally, using a range of established methods. We will identify the molecular determinants of their differential restriction activities, determine the range of viruses restricted, and describe in vitro the phenotypes of known human IFITM polymorphisms. Aim 2 seeks to understand the mechanism by which IFITM proteins restrict viral entry. Here we will use live-cell imaging to localize the site of restriction, and affinity- and shRNA-based approaches to identify cellular targets and cofactors of IFITM- mediated restriction. Aim 3 evaluates the in vivo contribution of IFITM proteins to the control of IAV, using two sets of knockout mice, lacking either the Ifitm3 gene alone or five Ifitm genes. These mice will be challenged with infectious IAV in the presence and absence of type I and II interferons, monitored for immune responses and clinical symptoms, and characterized post-mortem for pathological differences. Aim 1 and part of Aim 2 will be accomplished during the mentored (K99) phase of this proposal. The remainder of Aim 2 and all of Aim 3 will be accomplished during the independent (R00) phase. Summary. My goal is to develop a career as an independent investigator in innate immunity. My recent studies of the IFITM proteins will be the initial focus of these efforts. I am situated in a highly supportive and intellectually rich environment in which I can pursue my scientific and career development goals. PROJECT NARRATIVE Interferon-inducible transmembrane (IFITM) proteins are unique and critical effectors of the intrinsic and innate control of important human pathogens. The goal of this proposed research is to comprehensively understand the in vitro and in vivo activities of these proteins, with focus on their underlying cellular mechanisms.